Mammalian tissue culture cells, (strain PtKl), lysed at anaphase into a detergent, carbowax mixture move chromosomes poleward and elongate spindles at 50% in vivo rates for l0 min. Chromosome movement requires ATP and Mg ions. It is retarded by vanadate, a dynein ATPase inhibitor, or by the addition of high concentrations of tubulin. We are using the lysed cell model to study the function of the mammalian mitotic spindle and to identify the enzymes involved in chromosome movement. The lysed cell model will be used to study the nucleotide specificity and the role of calcium during anaphase. We will investigate the role of actomyosin during mitosis by lysing cells into NEM-modified heavy meromyosin (HMM). NEM-HMM binds irreversibly to actin even in ATP and blocks actomyosin interactions in model systems. We will study the role of microtubule polymerization and depolymerization during mitosis by lysing anaphase cells into high concentrations of tubulin, which promotes polymerization, or into colchicine-complexed tubulin, which blocks polymerization but not depolymerization. We will study the role of dynein in mitosis by: (l) further characterizing the vanadate sensitive component of the spindle; (2) using an antibody against dynein to localize dynein in the spindle; (3) adding physiologically relevant dynein to lysed mitotic cells. This information should contribute significantly to our understanding of how mitosis works at a cellular and molecular level.